(1) Field of the Invention
The present invention relates generally to a method for preventing or treating the development of respiratory allergies.
(2) Description of the Related Art
Allergy is defined as an “abnormal hypersensitivity to a substance which is normally tolerated and generally considered harmless.” The symptoms of allergies can range from a runny nose to anaphylactic shock. Nearly 50 million Americans suffer from allergic disease, and the incidence of these illnesses is increasing.
There are two basic phases involved with the allergic response. The first stage involves the development of the early phase of an immediate-type hypersensitivity response to allergens. The first time an allergen meets the immune system, no allergic reaction occurs. Instead, the immune system prepares itself for future encounters with the allergen. Macrophages, which are scavenger cells, surround and break up the invading allergen. The macrophages then display the allergen fragments on their cell walls to T lymphocytes, which are the main orchestraters of the body's immune reaction.
This cognitive signal plus several non-cognitive signals (e.g. cytokines) activate the naïve T-cells and instruct the T-cell differentiation into T-cell effector subpopulations. The key players in the allergic cascade are T-cells of the Th-2 phenotype (TH-2). TH-2 type T-cells are characterized by the secretion of several cytokines including interleukin-4 (IL-4), IL-5 and IL-13. The cytokines IL-4 and IL-13 then activate B lymphocytes which produce antibodies of the subclass E (IgE). IgE antibodies are directed against the particular allergen. The interaction of specific IgE antibodies on the surface of effector cells (mast cells and basophils) with an allergen triggers the early phase of immediate type hypersensitivity responses.
This mast cell activation usually occurs within minutes after the second exposure to an allergen. IgE antibodies on mast cells, constructed during the sensitization phase, recognize the allergen and bind to the invader. Once the allergen is bound to the receptor, granules in the mast cells release their contents. These contents, or mediators, are proinflammatory substances such as histamine, platelet-activating factor, prostaglandins, cytokines and leukotrienes. These mediators actually trigger the allergy attack. Histamine stimulates mucus production and causes redness, swelling, and inflammation. Prostaglandins constrict airways and enlarge blood vessels.
The second phase of the allergic immune response is characterized by infiltration of inflammatory cells, such as eosinophils, into the airways after an allergen exposure. An important linkage between sensitization and inflammation is represented by T-cells that secrete mediators not only involved in IgE synthesis, but also responsible for eosinophil recruitment, activation and survival. The tissue mast cells and neighboring cells produce chemical messengers that signal circulating basophils, eosinophils, and other cells to migrate into that tissue and help fight the foreign material. Eosinophils secrete chemicals of their own that sustain inflammation, cause tissue damage, and recruit yet more immune cells. This phase can occur anywhere between several hours and several days after the allergen exposure and can last for hours and even days.
Respiratory allergy is a particular type of allergy that affects the respiratory tract. The lining of the airway from the nose to the lungs is similar in structure and is often similarly affected by the allergic process. Therefore, an allergen that affects the nose or sinus also could affect the lungs.
For example, allergic rhinitis, also known as hay fever, is caused by allergic reactions of the mucous membranes in the nose and airway to allergens in the air. Symptoms of allergic rhinitis often include itchy nose, throat and eyes and excessive sneezing. Stuffy or runny nose often follow.
As allergens in one area of the respiratory tract can affect other areas of the respiratory tract, rhinitis in the nasal passages can lead to asthma, which is a much more serious illness that occurs in the lungs. Asthma is characterized by development of airway hyperreactivity, breathlessness, wheezing on exhale, dry cough and a feeling of tightness in the chest. Repeated allergen exposure can sustain the inflammatory immune response in the airways, resulting in a remodeling of the airways, commonly known as chronic asthma. Not everyone with allergic rhinits will develop asthma symptoms, but a significant number, especially those with recurring, untreated allergies, will show lung inflammation changes. About forty percent of people with allergic rhinitis will actually develop full-blown asthma.
If the nasal inflammation that accompanies allergic rhinitis reaches the sinuses, the result can be an uncomfortable infection called sinusitis, or rhino-sinusitis, in which the sinuses cannot empty themselves of bacteria. Symptoms include nasal congestion, runny nose, sore throat, fever, headache, fatigue and cough, as well as pain in the forehead, behind the cheeks, and even aching teeth and jaw.
Respiratory allergies are one of the most common afflictions of childhood. As with adults, respiratory allergies in children are most likely to appear in the form of allergic rhinitis and asthma.
The prevention of respiratory allergies is especially important in infants and young children, as it appears that early allergic sensitization to allergens is associated with a delay in the maturation of normal immune responses. Additionally, allergic sensitization is generally considered the first step in developing atopic disease. Baena-Cagnani, Role of Food Allergy in Asthma in Childhood, Allergy. Clin. Immun. 1(2):145-149 (2001). Frequently, asthma that begins early in life is associated with atopy, thus early allergic sensitization seems to play an important role in persistent asthma as well. Martinez, F., Development of Wheezing Disorders and Asthma in Preschool Children, Pediatr. 109:362-367 (2002).
Not only is there a strong association between allergic sensitization and asthma, but the association appears to be age-dependent. Although few children become allergen sensitized during the first few years of life, the great majority of those who do become sensitized during this period develop asthma-like symptoms later in life. Martinez, F., Viruses and Atopic Sensitization in the First Years of Life, Am. J. Respir. Crit. Care Med., 162:S95-S99 (2000). Thus, it is important to find ways to prevent early allergen sensitization and prevent respiratory allergies later in life.
There is increasing evidence that many aspects of health and disease are determined not only during infancy, but also during pregnancy. This is especially true with allergic disease, where immune responses at birth implicate intrauterine exposure as a primary sensitization event. For example, allergen-specific T-cells are already present at birth and early sensitization to food allergens are identified as predictors for later development of respiratory allergies. Illi, et al, The Natural Course of Atopic Dermatitis from Birth to Age 7 Years and the Association with Asthma, Clin. Exp. Allergy 27:28-35 (1997). In addition, lung development begins very early after fertilization and continues for at least two or three years after birth. Thus, both prenatal and postnatal airway development are important in the pathogenesis of respiratory allergy in infants and children.
It has also been shown that the human fetus develops IgE-producing B cells early in gestation and is capable of producing IgE antibodies in response to appropriate antigenic stimuli in a manner analogous to the well-recognized IgM responses that are observed in various prenatal infections. Weil, G., et al., Prenatal Allergic Sensitization to Helminth Antigens in Offspring of Parasite-infected Mothers, J. Clin. Invest. 71:1124-1129 (1983). This also illustrates the importance of preventing both prenatal and postnatal allergic sensitization to respiratory allergens.
Traditional medications for respiratory allergies include antihistamines, topical nasal steroids, decongestants, and cromolyn solution. As an alternative to traditional medications, probiotics have emerged as possible treatments for certain types of allergies.
Probiotic bacteria are living microorganisms that exert beneficial effects on the health of the host. Lactobacillus spp. and Bifidobacterium spp., which are normal inhabitants of the healthy intestine, are common species of probiotics. Unfortunately, there are very few published studies on the clinical effects of probiotic supplementation in infants. Agostoni, C., et al., Probiotic Bacteria in Dietetic Products for Infants: A Commentary by the ESPGHAN Committee on Nutrition, J. Pediatr. Gastro. Nutr. 38:365-74 (2004).
U.S. Patent App. No. 20040208863 to Versalovic, et al. is directed to a compound which has anti-inflammatory activity and is secreted from lactic acid bacteria. The application describes the use of Lactobacillus GG (LGG) to inhibit pro-inflammatory cytokine production. The reference however, focuses on adult models and does not disclose or suggest that the administration of LGG during pregnancy or infancy would be beneficial.
U.S. Pat. No. 6,506,380 to Isolauri, et al., describes a method of suppressing food-induced hypersensitivity reactions in patients suffering from food allergy by administering to them a probiotic. The reference does not, however, disclose the use of probiotics to treat respiratory allergies. Additionally, although the patent does discuss the treatment of infants with probiotics, it does not disclose the importance of treating both pre- and postnatally.
Several studies have focused on the pre- and postnatal administration of probiotics to prevent certain allergies in infants and children. For example, one study concludes that probiotics, administered during pregnancy and breast-feeding, might confer protection from atopic eczema for the infant. Rautava, S, et al., Probiotics During Pregnancy and Breast-Feeding Might Confer Immunomodulatory Protection Against Atopic Disease in the Infant, J. Allergy Clin. Immunol. 109:119-121 (2002). While the study found that fewer infants in the probiotic group developed atopic eczema than did the placebo group, the study concluded that the administration of probiotics had “no effect on the traditional objective correlates of atopy and atopic disease (i.e., skin prick test results and serum IgE antibodies).” Thus, because the traditional markers of atopy were unaffected by the probiotic supplementation, it must be assumed that the probiotic administration was effective only for atopic eczema and not for all allergies.
Similarly, a 2001 study concluded that probiotics can prevent atopic eczema, but that “concentration of total IgE and frequencies of increased antigen-specific IgE concentrations and of positive reactions in skin-prick tests were very similar between probiotic and placebo groups.” Kalliomaki, M., Probiotics in Primary Prevention of Atopic Disease: a Randomised Placebo-Controlled Trial, Lancet 357:1076-79 (2001). Again, these results suggest that the probiotic administration, while effective for atopic eczema, would not necessarily be effective for other types of allergies.